DS is 17mo and he hits, pulls hair and pinches. It's quite painful and he also does it to his 4.5yo sister who gets very upset about it. He also hits the dog and the cat so we've had to separate them for now. He doesn't seem to do it at nursery where he goes 5 mornings a week.
I've tried talking to him and explaining it hurts, doesn't seem to make a difference. I've tried distracting him but he switches to hitting me. I've tried putting him outside the room away from all of us for a short period (40 seconds?) but he goes off and plays with something else and as soon as I let him back in, explain why he was put in another room, etc he just hits again. I am now trying holding him in my lap until he calms down but he is quite strong and throws himself about.
The thing i found made the most difference was not saying "Don't hit" but rather saying "Be gentle... like this" and demonstrating what DD should do. Hope that makes sense?
I think 17 mo is probably a bit too young to understand being put outside the room, explanations about it hurting etc. I would certainly put him down on the floor if he hits though, and then do the "be gentle...like this" thing.